Speaker construction



Dec. 26, 1961 c. A. SWANSON 3,014,997

SPEAKER CONSTRUCTION Filed March 6, 1957 2 Sheets-Sheet 1 .ZEYVEJYTUF CARL A. SWANSON 1951 c. A. SWANSON 3,014,997

SPEAKER CONSTRUCTION Filed March 6, 1957 2 Sheets-Sheet 2 IHVEJUTQP CARL. A.SWANS ON Unite States This invention relates to a speaker construction and more particularly to a speaker of the type in which a voice coil is movable in an annular air gap of a magnetic structure and is connected to a cone or diaphragm. The voice coil is connected to an external circuit which may supply electrical power to cause vibration of the voice coil and subsequent vibration of the cone or diaphragm for the generation of compressional waves, or in the alternative, the external circuit may respond to an electrical signal generated in the voice coil by vibration of the diaphragm in response to sound waves. This application is a continuation-in-part of my copending application Serial No. 585,693, filed May 17, 1956.

Heretofore, speaker constructions of this type have included an annular centering disc for positioning the voice coil. It has heretofore been proposed to connect the voice coil with the external circuit by means of fine wires extending across the centering disc. A disadvantage of this arrangement is that the installation of these wires presented as much difficulty and expense as even older constructions in which the voice coil wires were cemented manually to the diaphragm. Another form of construction is the provision of conductive paths of metallic paint on the centering disc for electrically connecting the voice coil and the external circuit as disclosed in my copending application referred to above. Such an arrangement has many advantages but has a disadvantage in that the metal particles forming the path havea tendency to flake due to the continuous vibration of'the centering disc. In addition, it is necessary to use an expensive metal such as silver in order to obtain an impedance which is low in comparison to the impedance of the voice coil and even then the lead impedance is substantial.

Accordingly, a principal object of the invention is to provide a simple yet efiicient and effective method and arrangement for connecting a voice coil to an external A further object of the invention is to provide a voice coil connection arrangement which is reliable in operation and in which the generation of spurious sounds is precluded.

Briefly, this invention provides a method and means for connection of a voice coil to an external circuit in which the voice coil is sprayed with a molten ductile conductor atent v permanent magnet 21 FIGURE 1 is a side elevational view of a speaker constructed in accordance with the principles of this invention;

FIGURE 2 is an enlarged sectional view taken substantially along line II-II of FIGURE 1;

FIGURE 3 is a plan view of the speaker of FIGURE 1 partly broken away for the sake of clarity;

FIGURE 4 is an enlarged elevational sectional view taken substantially on line IVIV of FIGURE 3;

FIGURE 5 is a greatly enlarged fragmentary view showing the relationship of the metal strip to the tabs forming a part of the present invention;

FIGURE 6 is a diagrammatic view ofa metallizing gun of the type which may be utilized to apply conductive strips according to the present invention.

As shown on the drawings:

Reference numeral 10 generally designates a speaker constructed according to the principles of this invention. The speaker 10 comprises a frame 11 having a rim portion 12 from which the peripheral edge of the cone or diaphragm 13 is flexibly supported. The frame 11 has a substantially frusto-conical portion 14 which converges from the rim 12 to an annular base portion 15 on which a magnetic structure 16 is mounted.

The. magnetic structure 16 comprises a generally rectangular frame of magnetic material including a wall portion 17 secured against the base portion 15 of the frame 11, a Wall portion 18 in spaced parallel relation to the portion 17, a side wall portion 19 formed integrally with the portions 17 and 18 and confronting wall portions 20 and 20a completing the frame and connecting the ad jacent ends of the portions 17 and 18. A cylindrical has one pole in engagement with the portion 18 with its other pole engaging a cylindrical pole piece 22, preferably of soft iron or the like, which extends into a circular opening'23 in the portion 17 to define annular air gap 24. A dust cap or ring of nonmetal to form thin flexible metal strips of extremely low resistance bonded to the centering disc. According to a specific feature of the invention, thecentering disc is formed with a pair of circumferentially spaced outwardly radially extending tabs and the centering disc and tabs are sprayed with the molten ductile conductor metal which forms strips conforming generally to the configuration of the centering disc and the tabs and forms conductive paths between the voice coil and the external circuit.

A still further object of the present invention is to provide a novel loudspeaker construction in which the terminals for the external circuit may be positioned on the loudspeaker frame for convenient mounting of the external circuit leads.

Other objects, features and advantages will become more fully apparent from the following detailed descrip tion taken in conjunction with the accompanying drawings which illustrate preferred embodiments, and in which:

magnetic material such as brass is supported by the pole piece 22 to engage the outer surface of the portion 17 about the opening 23.

A voice coil assembly 26 is secured in a central open ing of the cone or diaphragm 13 and extends into the air gap 24. The illustrated voice coil assembly comprises a voice coil 27 of wire which is wound on a bobbin cylinder 28 of paper or other insulating material. In the alternative, the Wire could be of square cross-section or of a ribbon shape which might be wound either on a tubular form or might be constructed in a manner to be self-supporting.

The voice coil assembly 26 is maintained in coaxial relation to the pole piece 22 by means of a centering disc 29 having a peripheral edge portion 30 secured in any suitable manner, such as cementing or the like, to'the annular base portion 15 of the frame 11. The centering disc 29 is desirably foraminous and may take the form of woven textile material. The disc- 29 may have an nular corrugations 31 to increase the flexibility thereof with respect to axial movement of the voice coil assembly 26 while maintaining sufiicient rigidity to assure uniform spacing of the air gap 24.

According to the present invention, the disc 29 is provided with a pair of circumferentially spaced radially outwardly extending tabs 32 and 33, which, as shown in FIGURE 4, are adapted to extend in parallelism with the inner wall of the frusto-conical section 14 of the frame 11. The tabs 32 and 33 are desirably electrically insulated from the wall of the frusto-conical portion 14 by means of a suitable insulating cement. At the outer ends of the tabs 32 and 33 are openings 36 through each of which passes an electrically conductive eyelet or grommet 37. Suitable insulating discs 37a are provided to insulate the grommets 37 from the frame 11. Connected to the outer ends of the grommets 37 are terminals 37!) for the external circuit.

According to the present invention, a conductive path is formed between end portions 34 and 35 of the voice coil wire 27 and the terminals 37b by means of a coating or strips 38 which may be sprayed onto the surface of the centering disc 29 and the tabs 32 and 33 by means of a metallizing gun 39, shown in FIGURE 6. The metal employed may be any suitable conductive metal and preferably takes the form of copper. During the spraying process, the molten metal is sprayed in such a manner that the strands of the disc 29 and the tabs 32 and 33 become embedded in the metal as shown in FIGURE 5. The coating or strip 38 extends between the end portions 34 and 35 of the voice coil wire 27 and the several grommets 37. The coating or strip 38 conforms to the configuration of the corrugations 31 and aids in maintaining the required rigidity of the disc 29 without interfering with the requisite free vibration.

The loudspeaker of the present invention may be assembled in several difierent ways. The strip 38 may be applied to the disc 20 and then the voice coil assembly 26 may be installed. The ends 34 and 35 of the wire 2'7 are then bent over the inner periphery of the disc 29 and then soldered to the inner ends of the strips 38. The voice coil assembly may then be cemented in place, the centering disc cemented in the frame 11, the insulators 37a positioned, the grommets 37 secured in position and the cone 13 installed. The grommets 37 engage the outer ends of the strips 38 and form a conductive path to the terminals 37b. If desired, the disc 29 may be positioned in the frame 11 before the strips 38 are formed.

Alternately, the voice coil assembly 26 may first be cemented to the dis-c 29 and the ends 34 and 35 of the voice coil bent around the inner edge of the disc 29 to overlie the inner marginal edge of the top surface thereof. The strips 38 may then be sprayed over the ends 34 and 35 and outwardly to the ends of the tabs 32 and 33, the disc 29 cemented in position on; the frame 11, the grommets 37 installed and the cone 13 mounted. In accordance with the concepts of the invention the disc 29 may be installed in the frame 11 before the strips 38 are sprayed.

The metallizing gun 39 shown in FIGURE 6 is of conventional type and is provided with hoses 50 and 52 for supplying a gas such as acetylene, propane or natural gas and oxygen respectively for melting a wire 54 fed at a predetermined rate of speed into a combustion chamber 56. Air under pressure sprays the molten metal outwardly through an opening 58. The gun 39 may be manipulated manually to spray the strips 38 from the inner edge of the disc 29 outwardly or vice versa. The tabs 32 and 33 may be diametrically opposed, as shown on FIGURE 6, to afford acoustical balance and to facilitate the application of the strips 38. The gun 39 may be fixed and the disc 29 moved relative thereto. If desired, the strips 38 may be formed by electrostatic spraying.

The strips 38 provide effective and reliable conductive paths between the voice coil and the terminals of the external circuit. The terminals 37b may be conveniently located in an exposed position on the frame 11 so that they are readily accessible for connection of the leads of the external circuit. This construction is particularly advantageous in loud speakers of the tweeter type in which no openings are provided in the frusto-conical portion of the frame. Desirably the distance between the gun 39 and the disc 29 during the spraying step is such that the molten metal is reduced in temperature suificiently that it is incapable of burningthe fabric of the centering disc 29. The strips 38 being formed of homogeneous ductile conductive metal such as copper, exhibit much greater resistance to fatigue than coatings heretofore known. Copper is characterized by a minimum of electrical resistance and it involves much less cost than the precious metals required for metallic conductive paints.

It will be readily understood that numerous variations and modifications may be accomplished without departing from the true spirit and scope and principles and novel concepts of the present invention. I, therefore, intend to cover all such modifications and variations as fall within the true spirit and scope of the novel concepts and principles of this invention.

I claim as my invention:

1. In an electro-acoustical transducer, a frame, a magnetic structure on said frame having an annular air gap, a voice coil assembly including a voice coil, a centering disc having an inner circular edge portion secured to said voice coil assembly and an outer peripheral edge portion secured to said frame to support said voice coil for movement in said air gap, said centering disc being formed of a foraminous insulating material, a pair of thin homogeneous strips of metal extending from said inner edge portion of said disc to said outer edge portion thereof, the metal of said strips filling the interstices of said foraminous disc to be integrally bonded thereto and to flex with said disc, means electrically connecting the inner ends of said strips to the ends of said voice coil, and means for connecting the outer ends of said strips to an external circuit.

2. In electro-acoustical transducer, 21 frame, a magnetic structure on said frame having an annular air gap, a voice coil assembly including a voice coil, a centering disc of insulating material having an inner circular edge portion secured to said voice coil assembly and an outer peripheral edge portion secured to said frame to support said voice coil for movement in said air gap, said centering disc having a pair of circumferentially spaced tabs extending radially outwardly from said outer peripheral edge portion thereof, a pair of strips of homogeneous conductive material on said disc extending from said inner edge portion of said disc to the outer ends of said tabs, means electrically connecting the inner ends of said strips to the ends of said voice coil, a pair of electrical terminals conductively engaged with the outer ends of said strips at said tabs, and insulating means supporting said terminals on said frame.

References Cited in the tile of this patent UNITED STATES PATENTS Great Britain Feb. 4, 1953 

